Various methods and apparatus are used commercially to sew upholstered articles. European Pat. No. 89200451.6 discloses a "Sewing device for mattresses or cushions". This European Patent describes a device, intended for sewing the edges of a mattress, consisting of a mobile support surface, a sewing machine, and an oscillating arm, which in cooperation with control elements rotate the mattress around one of the corners of the mattress while the mattress is being sewed. The device also uses sensors that detect the position of the mattress, as well as a control unit which activates a pneumatically driven oscillating arm. The pneumatically driven oscillating arm is activated as a result of signals issued by the sensors and received by the control unit.
Spanish Patent No. 9100056 which is attributable to the applicants of the present invention describes a "System for the sewing of trimmed units". The apparatus described in this patent consists of a sewing machine affixed to one side of a table, a variable speed reducer motor connected to a transmission unit which, in turn drives a conveyor belt placed upon the table on which is placed a mattress. Through the use of the variable speed reducer motor, three different sewing speeds are provided. The particular sewing speed used is dependent upon the portion of the mattress which is being sewn. Sensors such as photoelectric cells, provide information about the current position of the mattress and that information is used to select an appropriate sewing speed. The highest sewing speed is intended for sewing straight sections, a slower speed is used at the end of these straight sections when approaching corners, and a third speed is for sewing the corners. An electrically activated arm that rotates the mattress during the sewing of the curves is also described in this patent.
Spanish Patent no. 9301374, also attributable to the applicants of the present invention, describes a "Process for the handling and sewing the perimeter of trimmed units". This patent describes a sewing method and apparatus that utilizes linear and arcuate pusher element both of which protrude through the plane of a table. Through the longitudinal action of the linear pusher elements and the arcuate action of the arcuate pusher elements, a mattress or other article is pushed through a sewing machine. The linear pusher elements and arcuate pusher elements are driven by a drive means located below the plane of the table.